Acousto-optic device having wide diffraction angle, optical scanner, light modulator, and display apparatus using the acousto-optic device

ABSTRACT

An acousto-optic device having a wide range of diffraction angle and an optical scanner, a light modulator, and a display apparatus using the acousto-optic device are provided. The acousto-optic device includes a core layer having a periodic photonic crystal structure in which unit cells of predetermined patterns are repeated, a first clad layer on a first surface of the core layer, the first clad layer having a refractive index that is different from a refractive index of the core layer, a second clad layer on a second surface of the core layer, the second surface being opposite the first surface, the second clad layer having a refractive index that is different from the refractive index of the core layer, and a sound wave generator configured to apply surface acoustic waves (SAW) to the core layer, the first clad layer, the second clad layer, or any combination thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation application of U.S. application Ser.No. 13/585,293, filed Aug. 14, 2012, which claims the benefit under 35U.S.C. §119(a) of Korean Patent Application No. 10-2011-0085149, filedon Aug. 25, 2011, in the Korean Intellectual Property Office, the entiredisclosure of which is incorporated herein by reference for allpurposes.

BACKGROUND

1. Field

The following description relates to acousto-optic devices having a widerange of diffraction angle, optical scanners, light modulators, anddisplay apparatuses using the acousto-optic devices, and, for example,to acousto-optic devices capable of increasing a diffraction angle rangeor adjusting diffraction angle characteristics of an output light byusing a strong anisotropic refractive index that generates around aphotonic band gap of a photonic crystal, optical scanners, lightmodulators, and display apparatuses using the acousto-optic devices.

2. Description of Related Art

The acousto-optic effect serves to regularly change a refractive indexof light in a medium by changing degrees of compression and rarefactionof the medium using sonic waves or ultrasonic waves. The acousto-opticeffect may enable the medium to function as a phase grating. Thus, lightthat is incident to the medium may be diffracted according to theacousto-optic effect.

In addition, the medium that diffracts the incident light according tothe acousto-optic effect is generally referred to as an acousto-opticmedium. An intensity of light diffracted by the acousto-optic medium andangle at which the light is diffracted by the acousto-optic medium mayvary respectively depending on intensity and frequency of sound waves.Therefore, an acousto-optic device, in which a sound wave generator(e.g., an ultrasonic wave generator) is mounted on a surface of theacousto-optic medium, may be applied in a light modulator to modulate anamplitude of the light, or an optical scanner to deviate the light.

However, a natural acousto-optic medium may be limited with respect tooptical anisotropy and acousto-optic transformation rates. Therefore,acousto-optic devices using the natural acousto-optic medium may belimited with respect to the diffraction angle of the output light. Thatis, in related acousto-optic devices using the natural acousto-opticmedium, a width of a range of the diffraction angle is insufficient toprovide adequate modulation or deviation of the output light.

Therefore, when related acousto-optic devices are used in opticalscanners, light modulators, displays, and other similar systems, anadditional optical system is necessary in order to compensate for thelimited diffraction angle range. The inclusion of the additional opticalsystem may increase the size of the above-referenced systems or serve todegrade resolution in the above-referenced systems. Accordingly, thereis a need for developing acousto-optic devices having increaseddiffraction angle ranges. Research is actively being conducted involvingthe structuring of the acousto-optic medium in various shapes withinacousto-optic devices.

SUMMARY

In one general aspect, there is provided an acousto-optic device,including a core layer having a periodic photonic crystal structure inwhich unit cells of predetermined patterns are repeated, a first cladlayer on a first surface of the core layer, the first clad layer havinga refractive index that is different from a refractive index of the corelayer, a second clad layer on a second surface of the core layer, thesecond surface being opposite the first surface, the second clad layerhaving a refractive index that is different from the refractive index ofthe core layer, and a sound wave generator configured to apply surfaceacoustic waves (SAW) to the core layer, the first clad layer, the secondclad layer, or any combination thereof. The core layer, the first cladlayer, the second clad layer, or any combination thereof to which theSAW are applied includes an acousto-optic material.

The general aspect of the acousto-optic device may further provide thatthe acousto-optic material includes ZnO, ZnS, AlN, Al₂O₃, LiNbO₃, TiO₂,Si, SrTiO₃, or any combination thereof.

The general aspect of the acousto-optic device may further provide thatthe first clad layer, the second clad layer, or a combination thereof isair.

The general aspect of the acousto-optic device may further provide thatthe sound wave generator is disposed on a surface of the core layer, thefirst clad layer, the second clad layer, or any combination thereof.

The general aspect of the acousto-optic device may further provide thatthe core layer, the first clad layer, the second clad layer, or anycombination thereof to which the SAW are applied includes apiezoelectric material as the sound wave generator.

The general aspect of the acousto-optic device may further provide thatthe sound wave generator is on a side surface of the acousto-opticdevice.

The general aspect of the acousto-optic device may further provide thatthe periodic photonic crystal structure includes a periodic structure inwhich two or more materials having different dielectric constants areregularly arranged in a two-dimensional (2D) or a three-dimensional (3D)structure.

The general aspect of the acousto-optic device may further provide thatthe first and second clad layers have periodic photonic crystalstructures with equal periodicity to the photonic crystal structure ofthe core layer.

The general aspect of the acousto-optic device may further provide thatthe core layer includes dielectric particles arranged in a regularperiod structure, and air is filled between the dielectric particles.

The general aspect of the acousto-optic device may further provide thatthe core layer includes a dielectric substrate with dielectric particlesarranged in the periodic photonic crystal structure.

The general aspect of the acousto-optic device may further provide thatthe dielectric particles are formed of air or a dielectric material, thedielectric material having a refractive index that is different from arefractive index of the dielectric substrate.

The general aspect of the acousto-optic device may further provide thata region of the core layer in which an angular distribution of therefractive index becomes flat is at certain frequencies and wave vectorsof lights around a photonic bandgap.

The general aspect of the acousto-optic device may further provide thatthe core layer has an anisotropic refractive index distribution of apolygonal shape, in which refractive indices toward its vertexes aredifferent from refractive indices toward an intermediate portion ofsides of the refractive index distribution.

The general aspect of the acousto-optic device may further provide thatincident light proceeds to a vertex of the refractive index distributionof the core layer, and the SAW proceeds along a region where therefractive index distribution of the core layer is flat.

In another general aspect, there is provided an optical scanner,including a first acousto-optic device configured to diffract and/ordeflect light in a first direction, a second acousto-optic deviceconfigured to diffract and/or deflect light in a second direction thatis perpendicular to the first direction, and light-coupling device thatmakes light incident to the first acousto-optic device. Each of thefirst and second acousto-optic devices includes a core layer having aperiodic photonic crystal structure in which unit cells of predeterminedpatterns are repeated, a first clad layer on a first surface of the corelayer, the first clad layer having a refractive index that is differentfrom a refractive index of the core layer, a second clad layer on asecond surface of the core layer, the second surface being opposite thefirst surface, the second clad layer having a refractive index that isdifferent from the refractive index of the core layer, and a sound wavegenerator configured to apply surface acoustic waves (SAW) to the corelayer, the first clad layer, the second clad layer, or any combinationthereof. The core layer, the first clad layer, the second clad layer, orany combination thereof to which the SAW are applied includes anacousto-optic material.

The general aspect of the optical scanner may further provide asubstrate including the first and second acousto-optic devices, thefirst and second acousto-optic devices being adjacent to each other.

The general aspect of the optical scanner may further provide that thesound wave generator of the first acousto-optic device is on thesubstrate, and the sound wave generator of the second acousto-opticdevice is on an upper surface of the second acousto-optic device.

In yet another general aspect, there is provided a two-dimensional(2D)/three-dimensional (3D) switchable image display apparatus,including a display panel, and an acousto-optic device array on a frontsurface of the display panel, the acousto-optic device array beingconfigured to diffract and/or deflect images displayed on the displaypanel, the acousto-optic device array including acousto-optic devices,each of the acousto-optic devices including a core layer having aperiodic photonic crystal structure in which unit cells of predeterminedpatterns are repeated, a first clad layer on a first surface of the corelayer, the first clad layer having a refractive index that is differentfrom a refractive index of the core layer, a second clad layer on asecond surface of the core layer, the second surface being opposite thefirst surface, the second clad layer having a refractive index that isdifferent from the refractive index of the core layer, and a sound wavegenerator configured to apply surface acoustic waves (SAW) to the corelayer, the first clad layer, the second clad layer, or any combinationthereof. The core layer, the first clad layer, the second clad layer, orany combination thereof to which the SAW are applied includes anacousto-optic material.

The general aspect of the 2D/3D switchable image display apparatus mayfurther provide that a height of each of the acousto-optic devices isequal to a height of one or more pixel rows of the display panel.

The general aspect of the 2D/3D switchable image display apparatus mayfurther provide that each of the acousto-optic devices extends in atransverse direction, and is arranged along a longitudinal direction.

The general aspect of the 2D/3D switchable image display apparatus mayfurther provide that each of the acousto-optic devices corresponds toone or more pixel rows of the display panel.

In still another general aspect, there is provided a holographic displayapparatus, including a light source configured to provide light, anacousto-optic device array including a plurality of acousto-opticdevices, each of the acousto-optic devices being configured to diffractand/or deflect the light provided from the light source, each of theacousto-optic devices including a core layer having a periodic photoniccrystal structure in which unit cells of predetermined patterns arerepeated, a first clad layer on a first surface of the core layer, thefirst clad layer having a refractive index that is different from arefractive index of the core layer, a second clad layer on a secondsurface of the core layer, the second surface being opposite the firstsurface, the second clad layer having a refractive index that isdifferent from the refractive index of the core layer, and a sound wavegenerator configured to apply surface acoustic waves (SAW) to the corelayer, the first clad layer, the second clad layer, or any combinationthereof, and a projection optical system configured to project the lightdiffracted by the acousto-optic device array. The core layer, the firstclad layer, the second clad layer, or any combination thereof to whichthe SAW are applied includes an acousto-optic material.

The general aspect of the holographic display apparatus may furtherprovide that each of the acousto-optic devices extends in a transversedirection, and is arranged along a longitudinal direction.

The general aspect of the holographic display apparatus may furtherprovide that the acousto-optic devices generate hologram rows in ahorizontal direction of a hologram image, and each of the acousto-opticdevices corresponds respectively to one or more of the horizontalhologram rows.

In an additional general aspect, there is provided an acousto-opticdevice, including a core layer including an acousto-optic material, thecore layer having a periodic photonic crystal structure in which unitcells of predetermined patterns are repeated, the core layer beingconfigured to generate a region at certain frequencies and wave vectorsof lights around a photonic bandgap in which an angular distribution ofa refractive index becomes flat, and a sound wave generator configuredto provide surface acoustic waves (SAW) along the flat region of theangular distribution of the refractive index in the core layer. Incidentlight proceeding toward a vertex of the angular distribution of therefractive index is diffracted along the flat region of refractive indexdistribution toward an adjacent vertex.

The additional general aspect of the acousto-optic device may furtherprovide a first clad layer on a first surface of the core layer, thefirst clad layer having a refractive index that is different from therefractive index of the core layer, and a second clad layer on a secondsurface of the core layer, the second surface being opposite the firstsurface, the second clad layer having a refractive index that isdifferent from the refractive index of the core layer. The sound wavegenerator is further configured to apply the SAW to the core layer, thefirst clad layer, the second clad layer, or any combination thereof. Thecore layer, the first clad layer, the second clad layer, or anycombination thereof to which the SAW are applied includes theacousto-optic material.

Other features and aspects may be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view illustrating an acousto-opticdevice according to an example embodiment.

FIG. 2 is a schematic perspective view illustrating an example of aphotonic crystal structure of a core layer in the acousto-optic deviceshown in FIG. 1.

FIG. 3 is a schematic plan view illustrating a photonic crystalstructure of a core layer in an acousto-optic device according toanother example embodiment.

FIGS. 4 and 5 are diagrams illustrating examples of equifrequencycontours of wavevectors in the wavevector space, which are related torefractive index distribution contours for propagating lights along acore layer having a periodic structure.

FIG. 6 is a diagram illustrating an example of a principle of usingrefractive index surfaces generated from the equifrequency contoursillustrated in FIG. 4 to increase a diffraction angle range.

FIG. 7 is a schematic perspective view illustrating operations of anacousto-optic device according to an example embodiment.

FIG. 8 is a schematic perspective view illustrating an example of anoptical scanner including the acousto-optic devices of the exampleembodiments.

FIG. 9 is a schematic diagram illustrating an example of atwo-dimensional (2D)/three-dimensional (3D) convertible image displayapparatus including the acousto-optic devices of the exampleembodiments.

FIG. 10 is a schematic diagram illustrating an example of a holographicdisplay apparatus including the acousto-optic devices of the exampleembodiments.

Throughout the drawings and the detailed description, unless otherwisedescribed, the same drawing reference numerals will be understood torefer to the same elements, features, and structures. The relative sizeand depiction of these elements may be exaggerated for clarity,illustration, and convenience.

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader ingaining a comprehensive understanding of the methods, apparatuses,and/or systems described herein. Accordingly, various changes,modifications, and equivalents of the systems, apparatuses and/ormethods described herein will be suggested to those of ordinary skill inthe art. Also, descriptions of well-known functions and constructionsmay be omitted for increased clarity and conciseness.

FIG. 1 is a schematic cross-sectional view illustrating an acousto-opticdevice 10 according to an example embodiment. Referring to FIG. 1, theacousto-optic device 10 includes a core layer 11, a first clad layer 12,and a second clad layer 13. The first clad layer 12 and the second cladlayer 13 are disposed respectively on an upper surface and a lowersurface of the core layer 11. A refractive index of the core layer 11 isdifferent from refractive indices of the first and second clad layers12, 13. For example, the refractive index of the core layer 11 may begreater or less than the refractive indices of the first and second cladlayers 12, 13. In this structure, light incident to the acousto-opticdevice 10 is captured between the first and second clad layers 12, 13,and proceeds along the core layer 11. Therefore, the acousto-opticdevice 10 may function as a waveguide of the incident light.

As noted above, the refractive index of the core layer 11 is to bedifferent from the refractive indices of the first and second cladlayers 12, 13. While there is no limitation in selecting materialsforming the core layer 11 and the first and second clad layers 12, 13,the core layer 11, the first clad layer 12, the second clad layer 13, orany combination thereof may be formed of an acousto-optic materialhaving an acousto-optic effect. When the core layer 11, the first cladlayer 12, the second clad layer 13, or any combination thereof is formedof acousto-optic material, a local density of the acousto-optic device10 may be changed in various forms, for example, repeatedly changedcorresponding to compression and rarefaction of sound waves applied tothe acousto-optic device 10. The acousto-optic material may be, forexample, ZnO, ZnS, AlN, Al₂O₃, LiNbO₃, TiO₂, Si, or SrTiO₃. In addition,the first clad layer 12, the second clad layer 13, or a combinationthereof may be formed of air.

In addition, the acousto-optic device 10 includes one or more sound wavegenerators 14, 15, 16, which may apply source waves to the core layer11, the first clad layer 12, the second clad layer 13, or anycombination thereof. For example, the sound wave generators 14, 15, 16may be electroacoustic modulators that generate surface acoustic waves(SAW) such as ultrasonic waves according to applied electric signals.Although the sound wave generators 14, 15, 16 are disposed on surfacesof the core layer 11, the first clad layer 12, and the second clad layer13 in FIG. 1, respectively, the sound wave generators may be disposed onthe core layer 11, the first clad layer 12, the second clad layer 13, orany combination thereof.

The core layer 11, the first clad layer 12, the second clad layer 13, orany combination thereof may function as a sound wave generator if formedof a piezoelectric material. For example, if the first clad layer 12 isformed of the piezoelectric material, when a voltage is applied to thefirst clad layer 12, the first clad layer 12 may vibrate and generateSAW. Otherwise, only one sound wave generator may be disposed adjacentto a side surface of the acousto-optic device 10.

According to the acousto-optic device 10, the core layer 11 may have atwo-dimensional (2D) or a three-dimensional (3D) regular photoniccrystal structure. The photonic crystal may be a periodic structure inwhich two or more materials having different dielectric constants (orrefractive indices) are arranged regularly. For example, the photoniccrystal may be a periodic structure having a periodicity of a submicronor less (e.g., a wavelength of light or less). The photonic crystal maytransmit, reflect, or absorb almost 100% of light of a certainwavelength band. In general, wavelength bands of light along certaindirections that may not transmit through the photonic crystal arereferred to as photonic bandgap. The photonic crystals having thephotonic bandgap are applied in various fields. The first and secondclad layers 12, 13 may have the same periodicity with that of thephotonic crystal structure of the core layer 11. However, the core layer11 may have the photonic crystal structure while the first and secondclad layers 12, 13 do not have the photonic crystal structure.

FIG. 2 is a schematic perspective view illustrating an example of aphotonic crystal structure of the core layer 11 in the acousto-opticdevice 10 shown in FIG. 1. Referring to FIG. 2, the core layer 11includes a dielectric substrate 11 a with dielectric particles 11 bbeing vertically oriented therein. For example, when the core layer 11is formed of the acousto-optic material, the dielectric substrate 11 amay include the acousto-optic material.

In FIG. 2, the dielectric particles 11 b of the dielectric substrate 11a are oriented perpendicularly to a surface of the dielectric substrate11. The dielectric particles 11 b of the dielectric substrate 11 a, asillustrated in FIG. 2, extend completely through the dielectricsubstrate 11 a. However, the dielectric particles 11 b of the dielectricsubstrate 11 a are not limited to or may stop short of extendingcompletely through the dielectric substrate 11 a. Further, thedielectric particles 11 b may be formed of air or a dielectric materialhaving a refractive index that differs from that of the dielectricsubstrate 11 a. In addition, the dielectric particles 11 b of thedielectric substrate 11 a are arranged in a periodic structure in whichsquare pattern unit cells are repeatedly arranged.

In another example embodiment, the dielectric substrate 11 a may beformed of air. In this example, the dielectric particles 11 b may beformed of a dielectric material that is not air (e.g., the acousto-opticmaterial). That is, the core layer 11 may include dielectric poles orparticles (e.g., the acousto-optic material) arranged between the firstand second clad layers 12, 13 in the regular periodic structure, and airbetween the dielectric poles or particles.

In addition, in FIG. 2, the dielectric substrate 11 a has dielectricparticles 11 b that are cylindrical. However, the dielectric particles11 b may have variable width that varies depending on a height. That is,a width of an intermediate portion of the dielectric particles 11 b maybe greater or less than widths at opposite end portions of thedielectric particles 11 b. Further, the dielectric particles 11 b may beconical. Moreover, the dielectric particles 11 b may have polygonalcross-sections, such as triangular or square cross-sections, as well asthe circular cross-section.

The photonic crystal structure of the core layer 11 shown in FIG. 2 isan example, and the photonic crystal periodic structure may have variousdesigns. For example, FIG. 3 is a schematic plan view illustrating a 2Dphotonic crystal structure of the core layer 11 in the acousto-opticdevice 10 according to another example embodiment.

Referring to FIG. 3, the core layer 11 may have a periodic structure inwhich hexagonal pattern unit cells are repeatedly arranged. Beside theperiodic structures shown in FIGS. 2 and 3, other various types ofperiodic structures may be used. For example, in replacement of thecylindrical dielectric particles 11 b, dielectric materials havinghexahedron or spherical shapes may be regularly arranged in thedielectric substrate 11 a. In addition, FIGS. 2 and 3 only show a 2Dphotonic crystal periodic structure; however, the core layer 11 may bedesigned to have a 3D photonic crystal periodic structure (that is, astructure having periodicities in transverse, longitudinal, and heightdirections).

The core layer 11 having 2D or 3D photonic crystals may be designed sothat a region may be generated around the photonic bandgap in which anangular distribution of the refractive index becomes flat. For example,FIG. 4 is a diagram illustrating an example of equifrequency contours ofwavevectors (k(ω)) of the lights flowing through the core layer 11having the photonic crystal periodic structure shown in FIG. 3. When thecontour distribution of the wavevector is divided by a wavenumber in theair (that is, 2π/λ, where λ denotes wavelength of light in air), thecontour distribution of the wavevector may be converted into refractiveindex distribution contours (i.e., index surface). In FIG. 4, thehexagonal dashed line denotes one unit cell (i.e., the first Brillouinzone) in a wavevector space for the photonic crystal structure shown inFIG. 3. In FIG. 3, ┌, M, and K denote main points of the wavevectorsthat represent symmetry. Referring to FIG. 4, the angular distributionof the refractive index becomes circular around the center (┌) of theunit cell in the wavevector space. This means that an isotropicrefractive index characteristic is shown around the center (┌) of theunit cell, that is, the refractive index is constant in any direction.On the other hand, the refractive index distribution is nearly hexagonalaround a boundary of the unit cell (near the photonic bandgap), asdenoted by a solid line. That is, six regions are generated around theboundary of the unit cell in which the angular distribution of therefractive index becomes flat. As a result, the refractive index of awavevector at a vertex (K) of the unit cell and the refractive index ofa wavevector at a center (M) in each side of the unit cell greatlydiffer from each other.

In addition, FIG. 5 is a diagram illustrating an example of contourdistribution (k(ω)) of wavevectors of the light flowing through the corelayer 11 having the photonic crystal periodic structure shown in FIG. 2.As described above, the contour distribution of the wavevector may beconverted into the refractive index distribution by the directions bybeing divided by the wavenumber in air. Referring to FIG. 5, in thephotonic crystal periodic structure shown in FIG. 2, the isotropicrefractive index characteristics, that is, the refractive index, isconstant in any direction around the center (┌) of the unit cell in thewavevector space is generated. The anisotropic refractive indexdistribution of square shape is generated around the boundary of theunit cell. In addition to the hexagonal and square anisotropicrefractive index distributions shown in FIGS. 4 and 5, the core layer 11may have various polygonal anisotropic distributions of the refractiveindex according to the design of the photonic crystal structure.

A range of diffraction angle of the light incident to the core layer 11having the periodic photonic crystal structure may be greatly changed byusing anisotropic refractive index distribution. FIG. 6 is a diagramillustrating an example of a principle of using the example refractiveindex distribution in FIG. 4 to increase a diffraction angle range.Referring to FIG. 6, in an isotropic structure in which the refractiveindex is constant in every direction, a maximum range of the diffractionangle of the light is θ1, even if the refractive index is regularlychanged in the medium by changing the degrees of compression andrarefaction in the medium using ultrasonic waves. However, in thephotonic crystal structure having a highly anisotropic refractive indexdistribution, when the incident light proceeds toward a vertex of therefractive index distribution, a SAW, such as an ultrasonic wave, isprovided that proceeds along the flat region of the refractive indexdistribution. As a result, the light may be greatly diffracted. Forexample, the light may be diffracted within an angle range of θ2 alongthe photonic bandgap region toward another adjacent vertex.

FIG. 7 is a schematic perspective view illustrating an example ofoperations of the acousto-optic device 10. FIG. 7 shows one sound wavegenerator 20 that is disposed on a side surface of the acousto-opticdevice 10 for convenience of description. However, the sound wavegenerators 14, 15, and 16 illustrated in FIG. 1 may be used. Referringto FIG. 7, when light L is incident to the acousto-optic device 10 alongan x direction, the sound wave generator 20 applies a SAW, such as anultrasonic wave, to the acousto-optic device 10 in a direction that doesnot coincide with the preceding direction of the light L, for example,in a y direction. Here, a periodic structure of the photonic crystals inthe core layer 11 may be oriented so that the incident light L mayproceed toward a vertex region of the refractive index distribution inthe core layer 11. In addition, the sound wave generator 20 may bedisposed so that the SAW may proceed along the flat region of therefractive index distribution in the core layer 11.

Then, the incident light L is diffracted. As a result, 0th-orderdiffracted light beam L0 and 1st-order diffracted light beam L1 isoutput. According to the acousto-optic device 10 of the exampleembodiment, when the SAW is applied to the acousto-optic device 10, thelight may be greatly diffracted while proceeding along the core layer 11due to the highly anisotropic refractive index of the core layer 11,because a diffraction angle range that satisfies constructiveinterference is increased. Therefore, the acousto-optic device 10 mayprovide a wider diffraction angle range than that of the relatedacousto-optic device.

Here, the diffraction angle may be defined as a difference betweenangles of the 0th-order diffracted light (i.e., just transmitted) beamL0 and the 1st-order diffracted light beam L1 by the acousto-opticdevice 10. The diffraction angle of the light and the intensity of thediffracted light may be controlled by the frequency and intensity of theSAW. In addition, the frequency and the intensity of the SAW may bedetermined by a magnitude and a frequency of an electric signal appliedto the sound wave generator 20. Therefore, the diffraction of the lightin the acousto-optic device 10 may be controlled by controlling theelectric signal applied to the sound wave generator 20.

The acousto-optic device 10 may be applied in various fields. Forexample, since the acousto-optic device 10 may adjust the intensity ofthe 0th-order diffracted light beam according to the diffraction degreeof the light, the acousto-optic device 10 may perform as a lightmodulator of the 0th-order diffracted light. Since the incident light isnot diffracted when the sound wave is not applied to the acousto-opticdevice 10, the incident light may transmit through the acousto-opticdevice 10 without a loss. However, when the incident light is diffractedby applying the sound wave to the acousto-optic device 10, 1st-order orother higher-order diffracted light beams are generated. As a result,the intensity of the 0th-order diffracted light beam transmittingthrough the acousto-optic device 10 is reduced. In addition, if moreenergy is allocated to the 1st-order or other higher-order diffractedlights according to the diffracted degree, the intensity of the0th-order diffracted beam may be further reduced. Therefore, theacousto-optic device 10 may function as a light modulator that modulatesthe amplitude of the 0th-order diffracted light beam.

In addition, the acousto-optic device 10 may be applied as an opticalscanner that deflects the incident light at a predetermined angle bychanging the diffraction angle of the 1st-order diffracted light beam.For example, when the acousto-optic device 10 having the wide range ofdiffraction angle is used in the optical scanner, an operating range(i.e., scanning range) of the optical scanner may be increased. As aresult, the configuration of the optical system used in the opticalscanner may be simplified. For example, an additional optical systemthat is used to increase the diffraction angle range in related opticalscanners might not be necessary.

FIG. 8 is a schematic perspective view illustrating an example of anoptical scanner 100 including the acousto-optic device 10 of the exampleembodiment. Referring to FIG. 8, the optical scanner 100 may include asubstrate 110, a first acousto-optic device 131 disposed in thesubstrate 110, a second acousto-optic device 132 disposed in thesubstrate 110 to be adjacent to the first acousto-optic device 131, alight-coupling device 120 making the light incident to the firstacousto-optic device 131, a first sound wave generator 131 a providingthe first acousto-optic device 131 with SAW, and a second sound wavegenerator 132 a providing the second acousto-optic device 132 with SAW.

Although not shown in FIG. 8, similarly to the acousto-optic device 10shown in FIG. 1, the first and second acousto-optic devices 131, 132 mayrespectively include a core layer having the photonic crystal structure,and clad layers on upper and lower portions of the core layer. In FIG.8, the first sound wave generator 131 a is disposed on the substrate 110and the second sound wave generator 132 a is disposed on the secondacousto-optic device 132; however, the present embodiment is not limitedthereto. Locations of the first and second sound wave generators 131 a,132 a may be selected appropriately in consideration of the desireddirection of the SAW. For example, the first sound wave generator 131 amay be disposed on a side surface of the substrate 110 or an uppersurface of the acousto-optic device 131. Likewise, the second sound wavegenerator 132 a may be disposed on an upper surface or a side surface ofthe substrate 110.

In addition, a refraction lens is used as the light-coupling device 120in FIG. 8; however, various optical devices may be used as thelight-coupling device 120. For example, a prism, a diffraction gratinglayer, a Fresnel lens, or a micro-lens array may be used as thelight-coupling device 120.

As an example, the first acousto-optic device 131 may be disposed sothat the incident light may be deflected in a horizontal direction, andthe second acousto-optic device 132 may be disposed so that the incidentlight may be deflected in a vertical direction. That is, as shown inFIG. 8, the light incident to the first acousto-optic device 131 throughthe light-coupling device 120 may be deflected in the horizontaldirection. Then, the light deflected in the horizontal direction may bedeflected in the vertical direction by the second acousto-optic device132. Further, the light deflected in the vertical direction may then beoutput. Therefore, the optical scanner 100 may perform a scanning of theincident light in the horizontal direction, the vertical direction, or acombination thereof within a predetermined angle range by modulating themagnitude and frequency of alternating current (AC) voltage applied tothe first and second sound wave generators 131 a, 132 a. In the exampleshown in FIG. 8, the optical scanner 100 includes two acousto-opticdevices 131, 132; however, the optical scanner 100 may include oneacousto-optic device that scans the light only in the horizontal orvertical direction, or a plurality of acousto-optic devices scanning thelight in a direction. The optical scanner 100 may be applied in a laserimage projection apparatus or a laser printer.

In addition, the acousto-optic device 10 described above may be appliedto a 2D/3D switchable image display apparatus. For example, FIG. 9 is aschematic diagram illustrating an example of a two-dimensional(2D)/three-dimensional (3D) convertible image display apparatusincluding a plurality of the acousto-optic devices 10 of the exampleembodiments. Referring to FIG. 9, acousto-optic devices 210 having thesame height as those of one or more pixel rows of a display panel 200and extending in a transverse direction may be arranged on a surface ofthe display panel 200 to form an array along a longitudinal direction.Then, each of the acousto-optic devices 210 may deflect an imagedisplayed by respectively corresponding pixel rows of the display panel200 in a predetermined direction.

For example, if sound waves are not applied to the acousto-optic mediumin the acousto-optic devices 210, the image displayed by each of thepixels of the display panel 200 is not deflected and transmitted throughthe array of the acousto-optic devices 210. In this case, as shown in aleft side of FIG. 9, the 2D/3D switchable display apparatus may operatein a 2D display mode. On the other hand, in a multi-viewpoint displaymode or a 3D display mode, each of the acousto-optic devices 210 maydeflect the image displayed from each of the pixels to generate beams ina plurality of directions. For example, a portion of the acousto-opticdevices 210 may deflect the image to a right eye of a viewer, andanother portion of the acousto-optic devices 210 may deflect the imageto a left eye of the viewer. As an another example, at a certain momentof a frame time, the acousto-optic devices 210 may deflect the image toa right eye of a viewer, and at another moment of a frame time, theacousto-optic devices 210 may deflect the image to a left eye of aviewer. Then, as shown in the right side of FIG. 9, the viewer may see3D images.

The acousto-optic device 10 may be applied to a holographic 3D displayapparatus. FIG. 10 is a schematic diagram illustrating an example of aholographic 3D display apparatus 300 including the acousto-optic device10 of the example embodiments. For example, as shown in FIG. 10, theholographic 3D display apparatus 300 includes a light source 310, anarray of a plurality of acousto-optic devices 320, and a projectionoptical system 330. The light source 310 may be an array of a pluralityof laser beams such as red, green and blue colors. In addition, thearray of the plurality of acousto-optic devices 320 may be formed bymanufacturing a plurality of acousto-optic devices extending in atransverse direction, and arranging the plurality of acousto-opticdevices 320 to form an array along a longitudinal direction. Here, theacousto-optic devices 320 generate hologram rows in the horizontaldirection. Each of the acousto-optic devices 320 may correspond to oneor more hologram rows in a hologram image displayed by the holographic3D display apparatus 300. The hologram rows diffracted by the pluralityof acousto-optic devices 320 may be projected on a predetermined spaceby the projection optical system 330 to generate the 3D image.

A number of examples have been described above. Nevertheless, it will beunderstood that various modifications may be made. For example, suitableresults may be achieved if the described techniques are performed in adifferent order and/or if components in a described system,architecture, device, or circuit are combined in a different mannerand/or replaced or supplemented by other components or theirequivalents. Accordingly, other implementations are within the scope ofthe following claims.

What is claimed is:
 1. An acousto-optic device, comprising: a core layerhaving a periodic photonic crystal structure in which unit cells ofpredetermined patterns are repeated to generate different refractiveindex distributions upon application of an acoustic wave; a first cladlayer on a first surface of the core layer, the first clad layer havinga refractive index that is different from a refractive index of the corelayer; and a sound wave generator configured to apply surface acousticwaves (SAW) to at least one of the core layer and the first clad layer,wherein the core layer and the first clad layer to which the SAW areapplied includes an acousto-optic material, wherein the core layer hasan anisotropic refractive index distribution of a polygonal shape, inwhich refractive indices toward its vertexes are different fromrefractive indices toward an intermediate portion of sides of therefractive index distribution.
 2. The acousto-optic device of claim 1,further comprising a second clad layer on a second surface of the corelayer, the second surface being opposite the first surface, the secondclad layer having a refractive index that is different from therefractive index of the core layer, wherein a sound wave generatorconfigured to apply surface acoustic waves (SAW) to at least one of thecore layer, the first clad layer, and the second clad layer.
 3. Theacousto-optic device of claim 2, wherein the second clad layer includesan acousto-optic material.
 4. The acousto-optic device of claim 3,wherein the acousto-optic material comprises ZnO, ZnS, AlN, Al₂O₃,LiNbO₃, TiO₂, Si, SrTiO₃, or any combination thereof.
 5. Theacousto-optic device of claim 2, wherein the first clad layer, thesecond clad layer, or a combination thereof is air.
 6. The acousto-opticdevice of claim 1, wherein the periodic photonic crystal structureincludes a periodic structure in which two or more materials havingdifferent dielectric constants are regularly arranged in atwo-dimensional (2D) or a three-dimensional (3D) structure.
 7. Theacousto-optic device of claim 6, wherein the first clad layer has aperiodic photonic crystal structure with equal periodicity to thephotonic crystal structure of the core layer.
 8. The acousto-opticdevice of claim 1, wherein the core layer comprises dielectric particlesarranged in a regular period structure, and wherein air is filledbetween the dielectric particles.
 9. The acousto-optic device of claim1, wherein the core layer comprises a dielectric substrate withdielectric particles arranged in the periodic photonic crystalstructure.
 10. The acousto-optic device of claim 9, wherein thedielectric particles are formed of air or a dielectric material, thedielectric material having a refractive index that is different from arefractive index of the dielectric substrate.
 11. The acousto-opticdevice of claim 1, wherein a region of the core layer in which anangular distribution of the refractive index becomes flat is at certainfrequencies and wave vectors of lights around a photonic bandgap,wherein the core layer has an anisotropic refractive index distributionof a polygonal shape, in which refractive indices toward its vertexesare different from refractive indices toward an intermediate portion ofsides of the refractive index distribution.
 12. The acousto-optic deviceof claim 11, wherein incident light proceeds to a vertex of therefractive index distribution of the core layer, and wherein the SAWproceeds along a region where the refractive index distribution of thecore layer is flat.
 13. An acousto-optic device, comprising: a corelayer; a first clad layer on a first surface of the core layer, thefirst clad layer having a refractive index that is different from arefractive index of the core layer; and a sound wave generatorconfigured to apply surface acoustic waves (SAW) to at least one of thecore layer and the first clad layer, wherein the core layer and thefirst clad layer to which the SAW are applied includes an acousto-opticmaterial, and wherein the first clad layer includes a periodic photoniccrystal structure in which unit cells of predetermined patterns arerepeated to generate different refractive index distributions uponapplication of an acoustic wave, wherein the core layer has ananisotropic refractive index distribution of a polygonal shape, in whichrefractive indices toward its vertexes are different from refractiveindices toward an intermediate portion of sides of the refractive indexdistribution.
 14. The acousto-optic device of claim 13, furthercomprising a second clad layer on a second surface of the core layer,the second surface being opposite the first surface, the second cladlayer having a refractive index that is different from the refractiveindex of the core layer, wherein a sound wave generator configured toapply surface acoustic waves (SAW) to at least one of the core layer,the first clad layer, and the second clad layer.
 15. The acousto-opticdevice of claim 14, wherein the first clad layer, the second clad layer,or a combination thereof is air.
 16. The acousto-optic device of claim13, wherein the periodic photonic crystal structure includes a periodicstructure in which two or more materials having different dielectricconstants are regularly arranged in a two-dimensional (2D) or athree-dimensional (3D) structure.
 17. The acousto-optic device of claim16, wherein the core layer has a periodic photonic crystal structurewith equal periodicity to the photonic crystal structure of the firstclad layer.
 18. The acousto-optic device of claim 13, wherein the firstclad layer comprises dielectric particles arranged in a regular periodstructure, and wherein air is filled between the dielectric particles.19. The acousto-optic device of claim 13, wherein the first clad layercomprises a dielectric substrate with dielectric particles arranged inthe periodic photonic crystal structure.
 20. The acousto-optic device ofclaim 19, wherein the dielectric particles are formed of air or adielectric material, the dielectric material having a refractive indexthat is different from a refractive index of the dielectric substrate.21. The acousto-optic device of claim 1, wherein the first clad layer,the core layer, or any combination thereof, are formed of apiezoelectric material.